Carburetor



Nov. 22, issz.

M FQENDLY CARBURETOR Filed Sept. 27, 1929 2 Sheets-Sheet I IILIIIFIIII ,IIIIIJ In VEHDF HEFEFTMEJZ/ i NGV. 22, 3.932. H M, FRIENDLY LSSSQ GARBURETOR Filed Sept. 27, 1929 2 Sheets-Sheet 2 5 l nVEnTDF-- Patented Nov. 22,l 1932 UNITED STATES PATENT OFFICE HERBERT FRIENDLY, OF CHICAGO, ILLINOIS;

TRUST COMPANY OF ILLINOIS, EXECUT MILTON S. FRIENDLY AND CENTRAL ORS OF SAID HERBERT M. FRIENDLY, DE-

CEASED CARBURETOR Application led September 27, 1929. Serial No. 895,487.

An object of the present invention is to improve the eiciency of carburetors used in gasolene engines, and internal combustion engines in general, particularly such as are employed for propelling automobiles, where they are operated under varying speeds.

With reference to the accompanying two sheets of drawings illustrating an exemplary embodiment of the present invention:

Fig. 1 shows a side view of a carburetor embodying the present invention.

Fig. 2 shows a top view along the line 2-2 in Fig. 1.

Fig. 3 shows a sectional View along the line 3-3 in Fig. 2.

Fig. l shows a preferred modification'of Fig. 3, when introduced into Fig. 3.

Fig. shows the well known air adjustment screw (used in the Marvel carburetor hereinafter identified) in section, which air adjustment screw is displaced by the air adjustment screw mechanism of the present invention.

For the purpose of disclosing the present invention, l have modified a well known carburetor by ythe introduction therein of the air adjustment screw inechanismembodying the present invention. This well known carburetor is the Model A-2-S Marvel carburetor, manufactured by the Marvel Carburetor Company, of Flint, Michigan.

In order to clearly point out the present invention, when embodied in the carburetor Model A`2-S referred to, the following parts of the said Model A-2S carburetor are identified by their recognized designations. The present invention, as incorporated in the said Model A2- S carburetor, will then be pointed out. j

The air flap-valve shaft is 9; the high-speed nor/.zie is 10;l the low-speed nozzle is 11; the low-speed venturi is 12; the air flap-valve is 13, shown in the approximate idling position; the throttle-valve is 14, shown in the idling position; the air inlet is 15; the throttle-lever is 16, shown in the idling position; the throttle-'lever adjusting screw for idling is 17; the stop for cooperation with said screw 17, is 18; the choke-valve lever is 19, shown in the normal idling position; the fuel .the carburetor is 31.

inlet is 20; the seasonal accelerating charge control lever is 21; the throttle operating rod is 22; the accelerator dash-pot piston is 23, shown dotted; the metering-pin for the highspeed nozzle is 24, shown dotted; the floatchamber is 25; the hand-operated throttlelever, operated from the drivers seat is 26; the dash-pot plunger-rod for controlling the air {lap-valve is 27 the air adjusting spring is 28; the dash-pot plunger is 29; the ratchetspring for retaining the adjustment of the l air adjustment screw is 30, and the screw for securing this ratchet-spring to the body of rThese parts in the embodiment containing the present invention are the same as employed in the well known carburetor, Model A-2-S referred to.

1t will appear that the present invention resides in the air flap-valve adjustment mechanism, and involves changing the tension ot the air adjustment spring 28 in a secondary manner, so as to make the air flap-valve 13 in a measure automatically compensated for the various degrees of throttle-valve openings, to promote delivering trom the carburetor a mixture of practically uniform richness; or at least a mixture more nearly approximating the ideal. f

It is well known that when adjusting carburetors of the Marvel type, and others o this general class, so that the motor will idle at a low equivalent mileage rate of travel of the automobile, and will at the same time not be subject to stalling easily when the throttle-valve is suddenly closed, that when the motor is operating at higher speed or the throttle-valve is more widely opened, as when negotiating a grade, the mixture delivered from the carburetor is inconsistently richer than when at idle speed or the throttle-valve isopened but slightly. The tenden'cy is to richen the mixture as the velocity of the air passing the nozzles supplying the fuel increases. The latter is partly true because of the well known phenomenon of Venturi tube action.

Heretotore, so far as I am aware, in order to insure that the motor would not stall easily, particularly when the throttle-valve would be suddenly closed, it has been necesaul sary to have the so-called idle mixture delivered by the carburetor excessively rich, so as to forestall critically low leanness of mixture resulting from suddenly closing the throttle-valve trom relatively open condition, as when momentarily idly racing the motor, or when operating the automobile at relatively high propelled speed, and then suddenly closing the throttle-valve. 'llhat is, suddenly closing the throttle-valve to idle position causes a dearth oit fuel supply through the nozzles, which dearth endures for a briei.3 time until the normal idle ejection oit the uel from the nozzles is recovered and the air Hap-valve has gained its equilibrium. lUnless there has been a margin of richness, by what may be conveniently termed an excess adjustment, provided tor in the idle adjustment, to off-set this momentary attenuation of the fuel mixture resultant from the sudden stoppage of the throttle-valve air delivery past the nozzles from the corresponding venturi, the motor will be apt to stall.

rllhis idle or normal adjustment referred to is made by varying the compression tension of the air adjustment spring 28 against the ldash-pot 29, which tension, in turn, is communicated through the plunger-rod 27 to the air tlap-valve 13. The air adjustment spring 28 is compressed responsive to the increased air pressure from the outside intake upon the air flap-valve 13 as the throttlevalve 1.4L opens and causes a greater degree ot vacuum to exist above the said air flapvalve.

When the air adjustment spring 28 is compressed strongly enough, based upon its idle adjustment, to properly and quickly seat the air Hap-valve 13 at such times as the throttle-valve is suddenly closed, as may be occasioned by the sudden stopping of the automobile, this strong compression tension, and particularly the said excess adjustment tactor of the air adjustment spring 28, operates to produce an unnecessarily rich mixture when the throttle is thereafter opened.

The present invention looks to automatically compensating the air flap-valve 13 for in turn automatically modifying the equivalent normal or idle compresslon tension set upon the air adjustment spring 28 only at onormal positions of the throttle-valve 14, in order to negate the said excess adjustment made for the temporary requirement at the time when the speeding motor returns to idle, and thus produce an oH-idle mixture leaner than would otherwise ensue if the idle adjustment of the air adjustment spring 28 were not modified in accordance with the od-normal openings of the throttle-valve in an approximate predetermined relationship. rllhe present invention may be said to comprise a means for altering the equivalent idle adjustment of the carburetor to a point below the critical value, only while the motor is operating oit-idle.

1t is possible, with thewell known Marvel Model A-2-S type carburetors referred to, to set the idle of the motor so that the throttle-valve lll will not close so far, and thereby increase the idle speed of the motor, and partly overcome the ditliculty of the motor stalling so readily when the 'throttle-valve 14 is suddenly closed to the idle position.

'lhis speeding up of the idle, as it is commonly termed, will admit diminishing the adjusted tension of the air adjustment spring 28 at idle, operating to keep the air {lap-valve 13 sufficiently tensioned towards its seated position, while at the same time admitting sufficient mixture of a somewhat leaner grade to pass into the motor. The mixture will be leaner because the air passing the nozzles will have a.` lower velocity, due to less restriction by the more highly tensioned air flap-valve 13. The mixture will also be leaner at all degrees of throttle-valve openings than would otherwise ensue with the air adjustment spring 28 normally tensioned more strongly against the air flap-Valve 13 at idle. Under certain adjustments last reterred to, an improved efficiency in fuel consumption will be attained.

However, drivers object to a fast idle of the motor, permitting a lighter normal idle tension adjustment ot the air adjustment spring 28 on the air tlap-valve 13, and the attending increased opening of the throttlel' valve 14 at idle. First, it causes more fuel to be consumed on idle operation, and this may odset the greater fuel economy under speed, particularly under the condltion of many stops being occasioned, where the motor will run idle more or less time. Second, the faster idle conduces towards overheating the motor. makes starting the automobile from standstill vmore diiiicult and trying for the driver, and the wear on the clutch will be increased, as well as increasing the attendant jar to the occupants of the car and to the propelling gear. But even under the condition of the faster idle adjustment, the fuel economy at the higher speeds will not be as high as is possible through the employment of the present invention, because no compensating adjustment of the air adjusting spring 28 at off-normal throttle-valve openings is provided tor in the said MarveltModel A--2- type carburetor.

'llhe present invention and its operation willbebest understood by first considering the employment of the Well known air adjustment screw shown in Fig. 5, with respect to the said-Marvel Model A-2-S carburetor, used in place of the air adjustment screw mechanism of the present invention shown in the assemblies Figs. 1, 2 and 3. The carburetor illustrated by the latter said figures Third, the tast idle the present invention.

will then become the referred to Marvel Model A-2-S type carburetor.

The air adjusting spring sioned by compression to a definite degree by turning the threaded adjustment screw Fig. 5. The air adjusting spring 28 rests against the inside unyielding seat of the air adjusting screw shown in Fig. 5, in the same relationship as it is shown resting in the yielding seat 33 in Fig. 3.

If the adjustment of the spring compr'ession tension on the air flap-valve 13 is then made proper for the desired idling speed, consistent with the throttle-valve idling setting, to insure that the motor will not be adjusted to stall too readily, then as the throttle-valve 14 is opened and the air passinginto the carburetor from the outside increases in quantity per unit of time, the air flap-valve will be flexed back on its shaft 9 as an axis against the tension of the air adjusting spring 28 to permit more air to pass. However., as the air adjusting spring 28 compresses and becomes stiffer in its tension, the restriction to the air passing the air flapvalve 13 will become greater, resulting in a higher velocity of this air, with an attendant increase in the fuel emitted from the nozzles 10 and 11. The latter referred to fuel emission increase is greater in proportion than the increase in the quantity of air passing into the motor. That is to say, the mixture becomes richer as the throttle-valve is opened. This then operates to lower the efficiency per unit of fuel with respect to the turns of the motor, as the speed or the throttle-valve opening increases, for moderate as well as high speeds, and this incidentally lowers the completion of combustion as a contributing factor of the loss of efiicienoy, so that more carbon will form in the combustion' chambers of the motor.

Tf it is now assumed that the air adjustment screw Fig. 5 is displaced by the air adj ustment mechanism of the present invention, as shown embodied in Figs. 1, 2, 3 and 4, it will appear that the air flap-valve 13 will be given a new operating characteristic or behavior when it is tensioned by the spring 28 for proper idle. This adjustment will be automatically varied in predetermined manner, as the throttle-valve is opened, by reason of the linkage with the throttle-valve operating gear, in one method of employing Another method of employing the invention, as will appear presently, effects this variation by tension spring poise.

rT'he air adjustment screw shell 32 of the present invention, which has threads for cooperation with the threads in the body portion of the carburetor corresponding to the threads of the air adjustment screw shown in Fig. 5, is provided with a yicldable seat 33 for the air adjustment spring 28. This seat 28 is now ten-` 33 is carried as a rigidly attached part of the movable stem 34, which stem fits slidably through the bearing-hole in the left end of j the air adjustment screw 32. A compression spring 35 is positioned on the inside of the air adjustment screw 32, concentric with the stem 34 in an annular groove 36 formed by the wall of the air adjustment screw and the gland forming the extension of the bearing for the stem 34. This spring 35 then servesl to make'the seat 33 yieldingly movable along the axis of the stem 34 and the aligned axis of the spring 28.

There is a collar 38 which may be set where desired on the stem 34. This collar is first to limit the inward movement of the stem 34 under the tension of the spring 35, which latter spring is stiff enough to insure that the right face of the collar 38 will be held against the face 39 of the air adjustment screw shell 32 as a stop, when the air adjustment spring 28 is compressed by turning the screw shell 32 until the proper idle is attained for the motor. This collar 38 is set by its set-screw after lthe stem 34 carrying the spring 35 has been inserted through its bearing hole. The location of collar 38 on the stem 34 is such that the proper play for the seat 33 in moving forward is provided for. This play may approximate three-sixteenths of an inch, tor example, although it will appear presently that the collar 38 also limits the actual rearward movement of the stem 34.

ln manufacture, the said play for the seat 33 will be standardized. It is desired to have this play for the seat 33 as small as is consistent with the possible requirements for radj ustment, so as to not have the air adjustment screw shell 32 longer over all than is necessary. Tt is thus clear that when the proper idle for the motor has been set by the air adjustment screw shell 32 being turned in or out to the proper point where it is held from turning freely by the ratchet-spring 30, the

collar 38 will be against the face 39 as a stop.

Therefore, the spring 35 need be only stltf enough to insure that the collar 38 will be held against the tace 39 under the condition of the motor idling.

Tt is noted, in this connection, that the f spring 35 has a portion of its turns at the center wound more closely than at the ends, being in this characteristic 'similar to the air adjustment spring 28, wherein this detail is quite clearly shown in the drawings Fig. 3. 1

This characteristic is to make the springs stiffer under extreme compression; at least stii'er as compressed from normall set condition with the motor idling, so thatthe unit space recession of the tree or compression end of the spring will be less as the unit compression pressure increases.

A. bracket 40, made of suitably formed sheet metal, or made integral with the body of the carburetor, carries a grooved idler spring 48 is secured to the clamp 45.

pulley 4l. lin the drawings showing this bracket non-integral with the body of the carburetor,- the bracket is secured to the body of the carburetor by passing the screw 3l through a suitably positioned hole in the bracket and then setting up the screw 31. 'llhe bracket thus mounts over the ratchet-spring 30 and fits over the boss holding the ratchetspring 30 out from the body portion of the carburetor. rlFhe bracket 40 is thus suitably formed to it over the top of the boss and ratchet-spring, While at the same time saddling the cylindrical surface or periphery of the portion of the carburetor body forming the neck 42, into which the air adjustment screvv threads.

i4 clamp 45, having screws 46 lits around the throttle-rod 22 and may be clamped securely and rigidly to the throttle-rod 22 at any desired place for the proper setting by saidscrevvs 46. A tightly coiled extension rllhe spring will not extend until after an appreciable pull has been exerted upon it, so that, as Will appear, the compression spring 35 Will b-e compressed to some extent, tensioned through spring 48, before the spring 48 will extend. ilhat is, the spring 48 will preferably, though not necessarily, act as a rigid link until a predetermined pull has been exerted through it to compress the spring 35, While causing the seat 33 to recede.

A. cord or other suitable link 50 connects from the attachment hole 51 near the free endof the stem 34 to the free end of the spring 48. llt is thus obvious that When the throttle-rod 22 moves to the right, in opening the throttle-valve 14, there Will be a tension applied through the spring 48 and lF cord 50 to the free end of the stem 34 to pull the said stem carrying the seat 33 to the left, increasing the compression tension of the spring 35. The latter said spring will yield so that the seat 33 Will move to the left with the stem 34 to Which it is rigidly fixed, and

lessen the tension that would otherwise bel applied upon theair flap-valve 13 by the spring 28. rllhat is to say, as the seat 33 recedes from its normal position under the incidental control of the throttle-rod 22, there vvlll be less consistent tension applied through, the plunger-rod 27 tending to hold the air flap-valve 13 seated, it being borne in mind that the tension of the spring 35 is sulicient to overcome the normally set tension of the sprlng 28, so that the collar 38 will be against the face 39 of the air adjustment screw shell 32, as a stop under idle operation.

'llhe cap 54 is threaded to cooperate with the threaded end of the air adjustment screw 32, as clearly shown in the drawings. rlFhe stem 34 passes through a slidable bearinghole in the center of the top of the cap 54.

llt `yvill thus appear that by adjusting the posltion of the 'cap 54 by turning it in or out,

s rasate@ that the distance the stem 34 can travel to the left Will be defined thereby. Thus, if the cap 54 is turned so that its inside face 55 reaches the left face of the collar 38, when in the drawn position, the stem 34 Will not be able to slide endivise, being .held rigid in the drawn position, and under this condition the seat 33 would be rigid and not alone able to alter the tension of the spring 28.

The cap54 has on its periphery a ratchetspring 56, suitably secured rigidly thereto, the free end cooperating With the fluted portion 57, so that when the cap 54 is set, the ratchet-spring 56 vvill prevent its revolving from jars of the automobile.

'llo adjust the carburetor, the cap 54 will preferably be screwed on until the collar 38 is clamped so that the stem 34 is rigid with the body ofthe air adjustment screw 32. rllhe threaded air adj ust-ment screw 32, having-the fluted portion 58 cooperative with the ratchetspring 30, is then turned in one or the other direction until the spring 28 exerts the proper tension on the air flap-valve 13 to give the desired idle performance of the motor, the motor being possibly raced somewhat and the throttle then suddenly released to determine the stability of the idle under the latter said condition. lln fact, the said adjustment, which may be termed the preliminary adjustment, for convenience, will be carried out through the agency of the adjustment of the air screw mechanism of the present invention as though the air adjustment screw lig. 5 were assumed substituted, rememberum ing that the stem 34 has no end play under the assumed condition, and is. in fact, then operatively equivalent to the screw shown in 1g. 5. j, After the idle adjustment has been made, Ml@ the cap screw 54 is turned out so that the stem 34 Will have end play, limited by the left face of the collar 38, with respect to the face 55, of an amount that Will be found most suitable. This latter may be ascertained by tryu@ ing the motor under operation. As the throttle-valve 14 is opened by the throttle-rod 22 moving to the right, the stem 34 will be pulled endWise against the compression ope position of the spring 35, the spring 48 also n@ extending as the spring 35 further compresses. ln view of the `fact that the end play of the stem 34 will be less than the movement of the throttle-rod 22, the spring 48 Will extend to permit this, the spring 35 compres- 312@ sing until the predetermined limit of movement of the stem 34 is reached when the left face of the collar 38 contacts with the'inner face of the cap 54. The spring 48 will thereafter extend as the throttle-rod 22 is 125 moved` to the right. lt is noted, in this connection, that the back pressure through the plunger-arm 27, as the throttle-valve is opened, will have the etl'ectof aiding in the compression of the spring 35.

ree

' from too freely opening.

Itis noted that the pre-set tension of the spring 28 will be modified with correspondence-to the recession of the seat 33, which recession will not necessarily be in constant like ratio with the movement of the throttle-rod 22, but on the other hand, will follow a characteristic determined by the design or characteristic of the springs and 48, which may be determined tentatively, in view of the behavior desired in the motor responsive to the movement of the throttle-rod 22, as well as upon the conditions the automobile is operated under and its inherent design.

The amount of endwise movement permitted for the stem 34 will be determined tentatively, but T have found that it may be approximately one-sixteenth of an inch. However, this will be governed by the conditions of operating the automobile and also by the characteristics of the air adjustment spring 28. So that this stated movement of the stem 34 may vary up and down from the stated approximation of movement. lf there is too much movement, it unduly lowering the power of the motor under oE-normal throttle-valve conditions, by making the mixture too lean, due to the` over-weakened tension of the air adjustment spring 28 not restraining the air flap-valve This amount of consistent movement will also be affected by j the set speed of `the idle.

llt will be noted that when the throttlevalve is suddenly released, the tension pulling the stem 34 to the left is released, so that the stem 34 will promptly move to the right until the right face of the collar 38 contacts with the face 39, at which position the maximum idling tension of the air adjustment spring 28 is manifested. llf the air flapvalve 13 has not yet seated and gained its equilibrium, this maximum idling tension will aid in more quickly attaining it.

lln order to conserve the efficiency of the dash-pot 29 within the air adjustment screw 32, so that the air fla -valve 13 will not be too sensitive in its equili rium, particularly as to any tendency to open further, and not be unduly affected by atmospheric pressure against the left side of the dash-pot 29 while a partial vacuum exists, the stem 34 will lit its bearing-hole without undue play and will Ybe as small in cross section as consistent with the required strength and stinfness, The ming imum air leakage will occur and the minimum friction will manifest itself under this condition.

Tt will be understood that the clamp may be positioned at any desired point on the throttle-rod 22, and therefore any desired degree of tautness or slackness of the cord ma exist at the idle position to meet the desired operating requirements. Under'certain operating conditions it maybe found desirable to not have any end pull applied will manifest itself in.

through the cord 50 to the stem 34 until the throttle has been opened a predetermined amount, while under other conditions it may be desired to have the cord 50 taut at the idle setting, while the right face of the collar 38 is against the face 39. The clamp 45 will be ositioned after the idle setting has been adjusted, although for slight alterations of this idle adjustment it will usually not be found necessary to change the position of the clamp 45, since the operation of the seatl 33 is not highly critical, while attaining advantages of the present invention, involvin the said seat 33 as a salient element thereo The preferred modification shown in Fig. 4 involves an operating rod 61 under the control of the driver, tensioned by the spring 62. This rod operates the collar member 63 which slides along the stem 34. Thus, if the driver wishes to prevent the stem 34 from moving to the left to thereby promote a richer mixture, he will depress the button 65 to move the collar to the right against the left face of the collar 38. This preferred embodiment involving Fig. 5 has been disclosed in a separate Fig. 4 to avoid involving the Figs. 1, 2, 3 unduly, and to make the preferred, comprehensive embodiment involving Fig. 4 more easily disclosed. Of course, the detail of the said preferred, comprehensive embodiment shown in Fig. 4 may be omitted without rendering the invention inoperative in its broader aspects, because the disclosure in Fig. 4 is merely an adjunct having the special use upon which the invention in its broadest claimed aspect does not depend.

While the eXampled form of the present invention discloses a cord 50 attached to the throttle-rod 22 for operating the stem 34 under the condition that the throttle-valve is being opened, it will be understood that any other gear for controlling the stem 34 under the condition of the throttle-valve being opened or the motor being increased in speed may be substituted.

Tt will be particularly understood, that while the exampled employment of the present invention to the Model lil-2 5 Marvel carburetor shows and describes means for operating the stem 34 carrying the seat 33 through the agency of the clamp 45, cord 50, idler pulley 41, and dependent directly upon the movement of the throttle-rod 22, this ear for operating the stem 24 from the throttle-rod 22 may not be necessary in certain applications of the present invention. That is, the stem 34 will be free to move and effect the compensation of the air flap-valve 13 solely by the control applied through the plunger-rod 27 from the air flap-valve 13, as will appear.

Under the last mentioned methodl of employing the invention, wherein the cord 50 is not attached to the stem 28, the tension of the spring 34 is adjusted by pulling the stern lll@ 3d outward to compress the spring 35 more,

or by allowingthe stem 3d to be drawn inward under the expanding tension of the spring 35 to thereby lessen this compression tension. 'llhe collar 38 is then set so that its right face rests upon the face 39 and the set screw in the collar is then set-up to make the collar (38) rigid with the stem 34k.,

"llhe tension of the spring 35, under the conn dition ot the proper idle adjustment of the spring 28 1s to be just strong enough so that this spring 35 will overcome the tension of the spring 28 and thus hold the collar 38 against the tace 39. 'llhat is, any further tensioning oi the spring 28 by screwing in the adjustment screw shell 32 will cause the collar 38 to unseat from the tace 39, llt will appear, then, that for the proper idle adjustinent ot the spring 28, it will be seated in the seat 33 in a xed position, to all intents and purposes, at the proper idle adjustment, while the motor is running at idle..

When the throttle-valve 1t is opened and the air hap-valve responsively swings back, the spring 28 will come under an added tension against its seat 33,- compressing the spring 35 more and thereby causing the collar 38 to unseat from the tace 39. 'lhe edect is, that when the increased back pressure reaches a certain valve which is applied through the plunger-rod 27, the two springs 28 and 35 are operating in tandem, whereas before the resence of the spring 35 in the edective adjustment was negated due to the tact that it was adjusted stid enough to retain the collar 38 against the seat 39, with a margin suilicient so that the left end of the spring 28 is, in edect, rigidly seated and thus divides the two springs 28 and 35` so tar as acting cooperatively. However, there is cooperative action of the two springs 28 and 35 when the margin of tension in the spring 35 causing the collar 38 to be seated on the tace 39 is overcome by the `further compression of the spring 28 responsive to the throttle-valve 14: opening from the idle position, in turn causmg the air Hap-valve 13 to swing to the lett.. 'l`he edect is that the long spring made up ot springs 28 and 35 in tandem will have less resisting power or opposition to the torce applied through the plunger-rod 27, than the sole spring 28. 'llhat is, the effect produced is as it the set idle tension on the spring 28 has been reduced, for the od-idle positions ot the air flap-valve 13 'llhe amount the air flap-valve 13 may swing to the left per unit ot' torce applied to it will be increased, prometing a leaner mixture, when the seat 33 starts receding to the lett.. The cap 5d will be positioned by turning it one way or the other to define the amount the stem 34C can move to the left betere being restrained by the collar 38 contacting with the tace 55, atter which the air flap-valve 13 will behave in accordance with the characteristic ot the sole incarne there is substantially no compression tension in spring 35 and they only eiiective compres sion tension is that in spring 28, while at the cti-idle position the tandemed springs 28 and 35 are both compressed., 'lhis permits a wider movement ot the air hap-valve 13 per unit of pressure applied thereby through the plunger-rod 27 as the springs 28 and 35 in tandem. compress until the presence ot the spring 35 is negated by the collar 38 contacting with the ace 55, than will be permitted while the air Hap-valve 13 is at the idle position where in the compression ot only spring 28 is actively edectiven rllhe .air flap-valve 13 will therefore be more stiy adjusted at the idle position thereof than at od-idle positions up to the point when the collar 38 contacts with thel tace 55..

While in the exemplary embodiment the spring 35 is a'compression spring, were the construction adapted to an extension spring operated by the stem 3d wherein said spring is wound close with the stated characteristic ot spring 4:8, the generally equivalent result would ensue.

While the present invention has been exemplitied by applying it with considerable detail to the Marvel Model .l-2 3 carburetor, it is to be understood that this has been merely by way of illustration, and that the invention is therefore not specic to this particular model ot carburetor., llt may be applied to other carburetors in the manner comlll@ prehended within the scope et the subjoined claims.,

ll claims- 1.1ln a carburetor provided with low speed and high-speed 'fuel jets, and an air valve opened bypressure ot air to operate the high-speed jet, an air valve spring for returning the valve to closed position when e the air pressure diminishes, and means for automatically decreasing the tension ot such spring for high speeds and increasing the tension tor low speeds..

2. ln a carburetor provided with lowspeed and high-speed fuel jets, and an air valve opened by pressure ot air to operate the high-speed jet, a spring for returning the valve to closed position when the air pressure diminishes, due to closing the throttle, a spring having one end ilexibly connected to the air valve, an adjustable seat tor the open end oit the spring, and means for moving the seat outwardly to decrease the opened by Lasefee tension of the spring when the throttle is open,

3. ln a carburetor provided with low-speed and high-speed fuel jets, and an air valve pressure of air to operate the high-speed jet, an air valve spring for returncrease the tension of the spring when the throttle is open, and spring means set to greater tension than the air valve spring for re-establishing the tension of such air valve spring to close the air valve firmly when the throttle is restored to idle position.

Ll. ln a carburetor ofl the class described, an adjustment screw mechanismv Jfor setting the air adjustment spring comprising a tubular screw-shell having a plunger-stem protruding from a closed end of said shell through a bearing-hole in the end of said shell, a plunger-seat for said spring fixed to said stem and positioned within said shell, a cap for the closed end of said shell through the top of which protrudes said stem, a stop adapted to be positioned rigidly on the protruding end of said stem, between the inner face of the cap and the end of said shell to form a front-stop and a back-stop, whereby the position said cap will have will determine the play said stem may have, a second spring concentric on said stem between said seat and the inside face of said end of the shell for tensioning said seat away from said inside face, a throttle valve operating gear and a link from said stem to the throttle-valve operating gear whereby when the throttlevalve is opened from idle position said stem will be drawn out of said shell within the limit of the back-stop to thereby oset by the recession of said seat the adjusted condition of the air adjustment screw, and will then re-position itself under control of said second spring within the limit of the frontstop its idle position, so that the tension of the air adjustment spring will be as set by said shell for idle operation.

5. ln a carburetor of the class described, an air flap-valve (13), an air adjustment screw (32), a yieldable spring-seat (33) carried by a stem (34), aA stop-collar (38), a cap (54) for determining the play of said stem and seat carried thereby, a spring (35) for tensioning the spring-seat inwardly, an air adjustment spring (28) compressed between the spring-seat and the air flap-valve for setting an idling tension on said valve by suitably positioning the air adjustment screw with respect to the body (42) of the carburetor, a throttle-valve operating gear, a link (50) for connecting the stem to the throttle-valve operating gear, whereby when the throttle-valve is operated from its idle position to a desired speed condition the spring-seat will be drawn back to ofl'set the tension of the air adjustment spring, and will again restore the tension oset when the throttle-valve is restored to idle condition.

6. ln a carburetor pro-vided with low speed and high speed fuel jets, a throttle-va ve, a flap-valve for selectively causing the low and high speed jets to predominate at different speeds, a spring for' normally positioning said Hap valve to render the high speed jet ineffective, and means for increasing or decreasing the tension of said'spring depending on the closed or open position of the throttlevalve respectively.

lln witness whereof, l hereunto subscribe my name this twentieth day of September,

HERBERT M. FRIENDLY.

when the throttle-valve is restored to 

